Floating weight electric switch



Feb. 14, 1939. R, 5 STONER 2,147,506

FLOATING WEIGHT ELECTRIC SWTCH Filed Nov. 3, 1936 3 Sheets-Sheet 1 lulllIII

Feb. 14, 1939. R. ssToNER FLOATING WEIGHT ELECTRICA SWITCH Filed Nov. 3,1936 3 Sheets-Sheet 2 lil n A (SEMI 7; (SUMQ WJ Feb. 14, 1939. R 5lSTONER 2,147,506

FLOATING WEIGHT LECTRIC SWITCH Filed Nov. 3, 1936 3 Sheets-Sheet 3 JMWROBERT 15mm-R, ,BY

@Ww SM www@ Patented Feb. 14, 1913s,?

Zdlidt maar otros Application November 3, 1936, Serlai No. 108,986

l t'lllims.

- having a weight oating upon a conducting liquid, the weight havingassociated therewith an armature which is adapted to be attracted by themagnetic forces produced by the energization of a coil, the uiddisplaced by the downward motion of the weight and armature being causedtcrise and engage a contact or electrode which is normally spaced apartfrom the liquid.

Another object is to provide a switch of the type described above,wherein the conducting liquid is of such a nature that it adheres to theelectrode during the upward motion of the float and downward motion cithe fluid, thereby causing the breaking of the circuit to take place notbetween the viiuid and the electrode but between different parts of theiluid itself. In this manner the wear and pitting ci the electrode,which ordinarily takesv'place, are effectively reduced or prevented.'

Another object is to provide a noot-operated switch wherein the iluidconsists of mercury having' other substances mixed therewith in such amanner as to form a mercury-like liquid, but

having the distinctive property of adhering to the electrode andof`being drawn out into a thin neck as the liquid surface moves lawayfrom the electrode. This thin neck not only causes the breaking of thecircuit to take place at a point away from the electrode, but alsoreduces the amount of current nowing across the neck at the instant ofthe break b'ecause oi the increase resistance of the small neck.

Another object is to provide an electric switch having a iloat operatedby a coil in such a manner as to displace a liquid upwardly intoengagement with an electrode, the liquid consisting principally ofmercury and a foreign substance, such as a. metal resembling lead, andpreferably forming an amalgam with the mercury.

Another object is to provide an electrode .for such a switch, theelectrode being of such a configuration asto enhance the adhering action(Cl. E-i12) of the conducting liquid, thereby increasing the facility offorming the narrow neck between adjacent portions of the 1iquid;

Another object is to provide a neat-operated electrical switch of such acharacter as to have a snap action, thereby bringing about the breakingof the circuit in a much quicker period of time than in ordinaryswitches.

Another object is to provide a motor starting circuit for split phasemotors employing a floatlo operated switch of such a character as torequire a lesser amount of current to hold the switch in engagement thanto close the switch in the rst place.

Another object is to provide a motor starting 1 circuit for c. splitphasemotor, wherein the floatactuated switch is provided with a.plurality of windings so that a light-duty push button may vbeemployed'in the circuit, one winding being used merely for closing theswitch and the other 20 winding being used for holding the switch in itsclosed position; one winding being automatically cut out as the otherwinding is energized.

Another object is to provide a method of breaking electrical circuitsconsisting of passing the electrical circuit through a conducting liquidl having an electrode capable of being immersed therein, the liquid andelectrode being of such al character that as they are moved apart fromeach other the liquid is drawn into a narrow 3 neck and subsequentlyseparates, thereby first reducing the amount of current owing throughthe neck because of the increased resistance thereof, and finallysevering the connection entirely.

In the drawings:

Figure 1 is a central vertical section through the switch of thisinventin, showing the parts in the position of rest, with' the operatingcoil unenergized. 40

Figures 2 to 5, inclusive, are views similar to Figure 1,-but showingthe successive stages of operationl of the switch.

Figure 6 is a side elevation ofthe switch shown in Figures 1 to 5,inclusive. 45

Figure '7 is a wiring diagram showing the switch of Figures 1 to 6,inclusive, employed in starting a split phase induction motor.

Figure' is a diagrammatic View of a mcdied switch having a plurality ofwindings, one Winding being employed for initially closing the switchand the other for holding the switchv in its closed position.

Figures 9 to 19, inclusive, are enlarged views, partly in section, ofvarious types of electrodes u employed in the switch shown in Figures 1-to 6, inclusive. l

Figure 20 is a central vertical section through a modified form ofswitch employing a spherical float.' l

Figure 21 is a central Vertical section through another modified form ofswitch employing a spherical float.

In general, the switch of this invention con` sists of a containerhaving a conducting liquid therein, an electrode normally spaced apartfrom the liquid, a ioat resting on the liquid, and a coil adapted whenenergized to attract the float and thereby to cause the level of theliquid to rise and engage the electrode, thereby closing the circuitbetween the liquid and the electrode. In particular, the liquid employedconsists principally of mercury with the addition of a foreignsubstance, such as lead, which causes the mercury to adhere to theelectrode rather than to be separated instantly therefrom, as is the-case with pure mercury.

Hitherto,` in switches employing mercury, it 1 has been necessary to useevacuated tubes and exceedingly pure mercury in order to avoid leaving askin-like layer of conducting foreign material between the electrode andthe liquid in its receded position. 'Ihe tubes were evacuated or lledwith an inert gas in order to prevent oxidation of the mercury and thesubsequent formation of such a layer of foreign material. This eect offoreign matter in a mercury switch employing a glass tubeshort-circuited the tube and rendered it useless for further action. Thepresent invention, however, deliberately utilizes mercury which is notonly not pure, but in contrast, has a foreign substance or "substancesadded thereto to give it a different eect.

When the ordinary pure mercury engages the electrode of the ordinaryswitch the latter merely pushes the mercury aside, and when the level ofthe mercury recedes it drops instantly away from the electrode vwithoutwetting it. In the present invention, however, the mercury mixture oramalgam adheres to the electrode and does not break away instantly. .Incontrast, the break of the circuit occurs not between the mercury andthe electrodel itself, as in switches hitherto made, but betweendiierentportions of the' mercury mixture at a point remote from theelectrode itself. o 'I'his construction adds to the life of theelectrode and' prevents wear and pitting.

A circuit is also provided wherein the switch' of this invention isemployed in starting a split phase induction motor,` the switch havingthe characteristic of requiring a smalleramount of current to hold it inits closed position than toclose it in the rst place. 'I'he switch ofthis invention .also possesses a snap action, which breaks the circuitwith' great rapidity when a breaking thereof, is desired.

Referring to the drawings in detail, Figure 1 shows one embodiment ofthe switch of this invention'as consisting of a lower casing portion Illhaving a downwardly extending reduced portion II, theportions I0 and IIbeing preferably 'of a non-magnetic material. The bottom of the portionII is closed by a plug I2, preferably of magnetic material, such as softiron. The reduced portion IIis surrounded by a winding forming a coilI3, having an insulating layer Il thereover. 'I'he leads I5 and I6 ofthis winding are brought out, respectively, to ring-like portions I1 andI8 (Figure 6) which may be engaged by suitable clips, forming no part ofthe present invention,

and facilitating the rapid insertion or remal of the switch.

'I'he central portion of the switch includes a` cylindrical casing I9 ofnon-conducting material, surrounded by the ring-like portions I 'l andI8 and terminating in a cap 20 of conducting material, having aring-like portion 2i for engagement by another clip, and an end portionZ2 having an aperture 23 for the reception of one end of an electrode24. The inner end of the electrode 26 is preferably enlarged, orotherwise provided with a portion` 25 vprojecting therefrom to enhancethe adhesion of the conducting material.

Arranged to reciprocate vertically within the casing portion I9 is aiioat 26 of annular form, and having an inner borg 21 within which isarranged one end of an armature 28 connected to the float by the arms29. The ends of the oat are preferably streamlined, as at 36 and Si, soas to permit the passage of the uid with the least resistance. Thearmature 23 is of magnetic material adapted to be attracted by the plugI2 when the latter is magnetized through the energization of the coilI3. The arms 29 are likewise-preferably streamlined to enhance thepassage of the fluid.

'I'he container, consisting of the portions` I9,

LIl and is, 1s pamauy nued with a uuid a2 of a foreign Vmaterial mixedtherewith, such as lead in the proportion of one part of lead to sixparts of mercury. These proportions, however, are not critical and otherproportions and materials may likewise be used to give the mercury anadhering effect upon the electrode.

'I'he electrode itself may be made in a number of different forms, suchas are shown in Figures 9 to 19, inclusive, in addition to the formshown in Figures 1 to 5, inclusive. In Figure 9 the electrode 33consists of a cylindrical rod with a at end 34. In Figure 10 theelectrode 35 has a rounded end 36. In Figure 11 the electrode 3l has apointed end 38. Inv Figure 12 the electrode 39`has a cup-shaped concaveend 40. In Figure 13 the electrode 4I has an enlarged head l2 with anannular depression 43 atthe back thereof. In Figure 14 the electrode 4Iof Figure 13 has been provided with a roughened surface 44 upon the head42. The electrode 45 shown in Figure 15 is provided with a solidenlarged head 46, with a roughened surface ll'I. The electrode i8 -ofFigure 16 has been provided with an enlarged conical head`49, with orwithout annular ridges 50 on the shank thereof. 'I'he electrode ofFigure 17, designated 5I, is provided with a reduced end portion 52,.with an `annular shoulder 53 separatingA the two portions of theelectrode. 'I'he electrode 54 shown in Figure 18 consists of a head 55having an annular groove 56 between it and It will be understood thatthe advantages of the invention are not limited to a liquid comprising amixture of mercury and lead. Other metals, such as antimony, bismuth andtin have been iound suitable for mixture with the mercury. It isadvisable, however, to employ for the electrode a material which willnot amalgamate with the mercury, otherwise, the electrode itself willdissolve somewhat in the course of time. The present invention makes useof this mixture of other substances with the mercury in order that theresultant liquid will adhere to the electrode and be drawn out into aneck-like form when the electrode and liquid are caused to move awayfrom each other.

It will be understood that the switch may be constructed without theiron plug I2 at the bottom thereof. The action would then be that of asolenoid I2 attracting the armature 28. The iron plug I2, however,intensifies and concentrates the magnetic action-of the winding I3.

Operation i I In the operation of the switch of this invention, thefloat 28 rests upon or near the surface of the liquid 32, depending uponthe buoyant characteristics. Under such circumstances, if the liquid 32consists of the mercury mixture described above, the surface of theliquid will be upwardly convex. When thewinding I3 is energized byclosing the electrical circuit including it, the resulting magneticfield set up attracts the armature or plunger 28. The force ofattraction is at first relatively weak, and increases in strength as thearmature 28 moves downwardly in response to the magnetic attraction.This isl especially true when the iron plug I2 is used to concentratethe magnetic action of the winding I3. This characteristic causes theswitch to have -a snap action so that the armature 28 is moving lveryrapidly as it approaches the downward limit of its motion. Meanwhile,the liquid displaced by the downward motion of the float 26 is forcedupwardly past the spider arms 29, and through the bore 21 intoengagement with the head 25 of the electrode 2l. This actionis shown inFigures 1 to 3, inclusive. Figure 1 shows the switch in its openposition with the various parts at rest. Figure 2 shows the switchslightly after contact has been made between the electrode and theliquid. Figure 3 shows the switch after a full contact has been made. l

The motion of the mercury itself also gives a snap action, correspondingwith the snap actionI of the armature 28 in moving downwardly into thewinding I2. By this action the mercury is mechanically hurled up towardthe top of the switch and into contact with the electrode by thedownwardly accelerated plunge of the oat. By reason of the mixture ofthe mercury with one or more other substances, as explained above, the

ymercury adheres to the electrode rather than the electrode being merelypushed into an indentation in the surface of the mercury, as is the casewhen pure mercury is employed.

When the circuit is broken the float 2B rises and the level of theliquid correspondingly drops. As the liquid surface recedes from theelectrode,

however', the adhesion of the liquid to the electrode causes the effectshown in Figure 4, whereby the liquid is drawn out into a neck-like formwhich becomes smaller and smaller as the liquid level falls. Thisnari-owing ofthe neck causes the electrical resistance thereof to beraised until only a small proportion of the current carried actionbecause the two portions of the liquid,

literally explode apart from one another at the instant of the break.The gas within the switch,

lwhich may be either air or inert gas, together with the vaporization ofthe mercury by reason of the heat produced at the point ci break, causethis explosive effect which results, in a suppression of the arc. Thiseect still further reduces the danger of pitting the electrodes or ofinjuring the various materials in the switch.

Thusfthe actual break occurs not at the'surface of the electrode, but ata point slightly below it. The break occurs between different portionsof the mercury, or other liquid, and not directly between the liquid andthe electrode, as in ordinary mercury switches. This action greatlyprotects the surface of the electrode and reduces the serious pittingeffect which occurs when pure mercury is used, as in ordinary switches.

As the level of the mercury recedes from its contact with the head ofthe electrode upon the deenergizationvof the winding I3, the mercurymixture or amalgam leaves the head 25 of the electrode with a rollingaction, and a crystallization-like effect is observed. Upon analyzingthe mercury mixture which is left upon the electrode head 25, it isfound that the proportion of foreign substances to the mercury is muchhigher than in the main body of the liquid. This foreign substancebecomes a granulated deposit upon the electrode and produces a muchfiner neck-like action, or a much finer thread of liquid as the surfacethereof recedes from the electrode. Thus, assuming lead to be the mixingsubstance, if the ratio of lead to mercury is one to six elsewhere inthe main body of the liquid, the ratio may be as much as one to one onthe electrode. This important effect increases the efficiency of theswitch without requiring a high mixture of 'foreign substance in themain body of the liquid iiirected to the same purpose of increasing theadhesion of the liquid.

Moreover, this thread-like or neck-like action which occurs when thecircuit is broken, enables the switch to carry a much higher currentthan is possible with ordinary switches where pure mercury is used, anda direct break is made between the surface of the'mercury and theelectrode surface. A switch of my invention may carry as muchas 50 to100 amperes of current, an amount much greater than an ordinary switchof the same size and employing pure mercury can carry. The reason forthis effect is as stated above. that the neck-like action greatlyincreases the resistance' across the switch and therefore reduces thecurrent actually flowing to a mere fraction of that flowing when theswitch is fully closed. The alloy or mercury mixture is drawn out into aform somewhat resembling a water spout. This separation of the point ofbreak from the electrode itself enablesthe use of a cheapmetal for theelectrode, as contrasted with the expensive tungsten or platinumnecessary for use with ordinary mercury switches where the break. occursdirectly at the surface `of the electrode. The break between different.portions of the amalgam or mercury mixture protects the electrodeitself to such an extent that an ordinary soft iron screw used as anelectrode has been successfully used to break the circuit of current of50 to 100 amperes without serious pitting over a considerable period oftime.

It will be observed, moreover, thatl the switch of the present inventionmay be operatedwithout evacuating the air as the latter does not createan adverse eect by its oxidation of the mercury. The question ofimpurities in the mercury is a serious problem in ordinary mercuryswitches, especially those employing glass tubes. As the mercury switchtilts, or lthe mercury otherwise moves, it tends to leave a trail ofimpurities between the electrode and the mercury surface, therebyshortcircuiting the switch. In the present invention, however, theseimpurities do not impede the action of the switch because the tube doesnot tilt, and a complete path of impurities is never made possible.

Furthermore, the action of the switch itself has a purifying eiect uponthe mercury mixture so that a clean surface `is always presented to theelectrode. In the action of the switch it is observed that although themercurymixture surface 'is completely coatedv with impurities, in theposition shown in Figure 1, by the time the mercury has risen to engagethe electrode these impurities have moved aside like a curtain. andpresented a brilliantly reecting mercury.l surface to the electrode.Moreover, the iioat 26 may be spaced with a considerable clearancebetween it and the side walls of the container I9 because the rising ofthe mercury itself into this space acts as a kind of lcushion-andspacing agent, prevventingv the sticking of the float to theside walls.This arises from the dlculty of passing'mercury throughlsmall aperturesand is very useful when the switch is employed in connection with dinarymetal, such as iron or aluminum is used,

the coating or oxide or other impurities which the metal may acquire, donot affect the switch adversely after a few closures thereof. It lhasbeenfound that with this mercury mixture instead of pure mercury themixture exerts an effect similar to tinning the electrode where it isimpure or coated with rust and like substances at the start of theoperation. Y

VIn addition to the foregoing qualities, this Vswitch possesses theadditional feature of releasarcanos ing eld windings 6l to' 61,

Improued switch. :mit for splitv phase motor circuits Y' Y Y In Figure 7there is shown a split phase motorcircuit having windings B0, 6I, 62 and63 and splitphase 'or starting windings 6d, 65, 66 and S1 arranged instaggered sequence between the windings 60 to 63,-inclusive. Thewindings 60 and 62, for example, are wound in an opposite direction fromthe windings 6I, and 53, whereas the windings 64 and G6 are wound in anopposite direction from the windings G and G7. The windings 60 to 83,inclusive, are led out to the lines 68 and SS, whereas the windings 64to S1, inclusive, terminate in the li'nes 'le vand. il. The

lines l@ and S8 are connected to one another, as

at l2, and terminate in the connection plug 13.

From the opposite terminal of this plug the line Il-i5.. To this ring ilis connected one lead of the coil or winding i3, the opposite end beingconnected to'the line 69. The line 'II is connected cury 32 and theelectrode 24 between the lines 'i4 and 69, thereby energizing thestarting wind ings 64, 65, 66 and 61, as well as the windings 60, 6|, 62and G3. `'Ihe motor then starts its rotation, and as it comes up tospeed the reverse 14 runs to the lower ring I I of the mercury switch Yelectro-motive force arising from opposing theA impressed current,causes the current in the switch winding I3 to drop steadily until atacertain deiinite speed approaching its full running speed (say 1500 R.P. M for a F150-R. P. M. motor), the current becomes insuflicient tohold the amature 28 against the buoyant effect of thel float 26 in themercury mixture 32.

Due to the fact that a greater amount of current is required to closethe switch than to re- V)lease and open it, a lag effect occurs inassociation with the main field and the starting eld.

The main. fleld'windlngs SII to El, inclusive, are usually of heavy wirewith a relatively low re- -sistance andhigh reluctance, whereas thestartinclusive, arranged 90 degrees in rotation therefrom, are of highresistance and low reluctance. As the current drawn by the 'motor dropsas it -increases its speed past the critical point where it isinsumcient to hold the mercury 'I5 in a closed posi-v tion, the switch'I5 opens, removing the starting vwindings El to 61inclusive, from thecircuit and leaving only the main eld windings 6 to p 63, inclusive. Theiron plug I2 intensies the magnetic action and can be varied in size andmagnetic characteristics in order to adjust the lag characteristicsarising from-this effect. The

motor continues to rotate under the eil'ect of its main windings 68 toG3 alone until it is stopped by opening the main switch 16. A When themain switch 'I6 is again closed the main and starting field windingsthen draw' the full amount of amperage possible, and the mercury switch'I5 is again closed. It'again remains closed until the motor speedreaches the critical point at which the current flowing through the coilI3 is insuflicient to hold down the armature 28, whereupon the switchagain opens and the main nexos ,5

operate without the starting elds, in the manner heretofore described.

Multiple winding mercury switch circuit The mercury switch circuit shownin Figure 8 is especially adapted for starting split phase motors andenables the use of light-duty starting and stopping switches, such asordinary push button `switches not particularly adapted to the passageof heavy current. For this purpose the .mercury switch 11 is providedwith a winding 18 of light wire and a winding 19 of heavy wire. Thelight winding 18 serves as a switch-closing winding and the heavywinding 19 as a holding winding for `holding the switch in a closedposition. The internal arrangement or the switch 11 is the same as thatshown in Figures 1 to 5, inclusive, except that the iron plug I2, heredesignated 88, is insulated by the insulating lportion 8| from theremainder of the portion I Connected to this end plug 88, which servesas an additional terminal on the switch, is the line 82 forming the leadfrom one end of the heavy winding 19, the other lead 83A of whichconsists of one of the power lines, an auxillary line 84 from whichleads to one terminal of the stopping push button switch 85. From theopposite terminal of the latter the line 88 runs to the lead 82 of theheavy winding or holding coil 19. From the line 88 the line 81 runs toone lead of the fine winding or closing coil 18, the opposite lead 88 ofwhich is brought out to one terminal of the starting push button switch89. From the opposite terminal of this switch the line 98 runs to jointhe line 9| interconnecting the windings of the motor 92 with theterminal 93 of the electrode'24. The remaining line 94 is the power lineleading to the motor 92. A line switch 95 makes and breaks the circuitbetween the lines 83 and 94 and the current mains 98 and 91,respectively.

In the operation' of the circuit shown in Figure 8, the general actionof the switch is as described previously. When the starting push buttonswitch 89 is closed the circuit is closed between the lines 98 and 88,thereby energizing the iine wire closing coil 18 by way of the lines 81,88, the stopping push button switch and the lines 84 and 83. Theenergization of the closing coil 18 attracts the armature 28 and iloat28,- and causes the mercury mixture 32 to riseand engage the electrode24, closing thev circuit between the terminals 93 and 88. When thisoccurs the current ilows from the line 91,` through the main switch 95,the line 94, the

motor 92, the line 9|, the terminal 93, the switch 11, the terminal 88,the line 82, the holding winding 19, the line 83 and the main switch tothe line 98. This energizes the holding coilv 19 and causes it to holdthe armature 28 and float 28 in their lower positions even when the pushbuttonswitch 89 is released by the operator.

The closing winding 18 -is therefore completely deenergized the instantthe operator releases ,the starting switch 89. Even though the operatorkeep the starting switch 89 closed, however, the

winding 18 is not endangered by the flow of heavy current because it isshunted out by the connection between the terminals 93 and 88 as soon asthe switch closes. Consequently, the circuit shown in Figure 8 dscapable of employing very light-duty switches and no damage can resultto the switches even if the operator keeps the push button switchesclosed for an appreciable period of time. The closing winding 18 is cutout automatically and instantly by the aotion of the holding winding 19as soon as the switch closes. It the operator depresses the stoppingbutton 85, however, the motor circuit is instantly broken as this actionbridges the ter minals of the holding coil, the deenergization of whichinstantly releases the amature 28 and float 28. Accordingly, no damagecan result to the windings even though the operator maintains thestopping switch 85 in a depressed position for an appreciable period oftime.

Ball float switch The modified switch shown in Figures 20 and 21 employsaball V98 within a cup-like casing 99 having mercury or a similarconducting liquid |88 therein. The side of the casing 89 is `pierced byelectrodes |8| and |82, insulated by the insulating portions |83 and |84from the casing 98. Optionally the casing 99 may itself be made ofinsulating and non-conducting material. A plug |85 closes the bottom ofthe casing 99 and a winding |88 surrounds this casing, the leads |81 and|88 being connected to a suitable source of electrical energy, in themanner previously described in connection with the other forms ofswitches.

The iioat 98 consists of a ball which is o! iron or which has an ironcore. If the ball is all of iron it is preferably coated with aninsulating coating, such as synthetic resin, hard rubber, etc. When thewinding |88 is energized the magnetic field thereby set up attracts thefloat 98, forcing it downwardly and causing the top surface |89 to riseto the point where it simultaneously immerses the electrodes |82 and|8|. This closes the circuit and causes the energizetion of the lines||8 and leading from the electrodes |8| and |82. The use of the balliloat 98 effectively prevents any sticking because it will roll up anddown the inner walls of the casing 99.

The switch shown in Figure 21 is similar to that shown in Figure 20except that the end plug ||2 replaces the terminal |82 and the terminal||3 replaces the terminal |84. H4 is energized, in a manner similar tothe winding |88, the iioat ||5 is forced downwardly into the mercury H8within a cup ||1, causing the mercury to overow into the space adjacentthe electrode H3. Accordingly, the circuit is closed between the line H8connected to the plug |12 and the line ||9 leading from the electrode||8.

Time delay' switch The switch shown in Figures l to 6,`inc1usive, can beemployed as a time delay switch by causing the apertures between thearmature 28 and the iioat 8| to be restricted in size so as to impedelthe free passage of uid therethrough. Under these circumstances,the/float and armature will not become operative to make or break thecircuit instantly after the coil I3 has become energized or deenergized,because the opposition onered by the small apertures adjacent the arms29 will exert a cushioning action by the mercury and retard the actionof the switch. In this manner the switch is given a dash pot actionwhich provides a time delay feature. It will be also observed that byreducing the clearance be- As the winding' coil I3 at the top of theswitch, so as to make the rendering said liquid adherent to saidelectrode switch'a normally closed instead of a normally open switchlike the switch in Figures 1 to'6, inclusive, the thus modiiied switchcan be used as a time delay' overload protection switch for electricalcircuits, especially where the mercury is made to pass throughrestricted orifices, as described above. Under these conditions thecurrent normally owing through the switch coil would be insuicient toopen this normally closed switch. When an overload of current passesythrough the coils, however, it will actuate the armature and iloat insuch a manner as to open the circuit between the mercury mixture and theelectrode. It, however, the surge is oi' merely momentary duration sothat the motor windings can carry it without damage, the dash pot actionof the mercury in passing through the restricted apertures, such asthose existing between the armature v28 and the float 3|, will interposea time delay before the switch can become operative to open the motorcircuit. This time delay is eilicient in preventing stoppages of themotor caused by momentary overloads whichthe motor windings canconveniently carry.

It will be understood that I desire to comprehend within this inventionsuch modications as come within the scope of the claims and theinvention.

. Having thus fully described my invention, what I claimas new anddesire to secure by Letters Patent, is:

1. In combination. a container, a conducting liquid in said container,an electrode, means associated with said container for selectivelycreating a magnetic field, and iloat means responsive to thecreation ofsaid magnetic field for displacing 'said liquid into engagement withsaid electrode, said liquid being adherent to said electrode to f\ormank elongated portion between said electrode and said liquid in responseto the separation o! said electrode and said liquid.

2. In combination, a containena conducting liquid in said container, anelectrode, means associated with said container for selectively creatingaV magnetic iield. and oat means responsive to the creation of saidmagnetic iield for displacing said liquid into engagement with saidelectrode, said liquid comprising a mixture of mercury and a materialrendering said liquid adherent to said .electrode and attenuable into aslender column upon the separation of, said electrode and said liquid.

3. In combination, a container, a conducting liquid in said container,an electrode, means assocated with said container for selectivelycreating a magneticiield, and oat means responsive to the creation ofsaid magnetic field for displacing said liquid into engagement with saidelectrode, said liquid comprising a mixture oi mercury and a materialamalgamatable therewith and attenuable into a slender column upon theseparation of said electrode and said liquid. 4..In combination, acontainer. a conducting i liquid in said container, an electrode, meansas` sociated'with said container for selectively creating a magneticeld, and float means responsive to the creation of said magnetic eld fordisplacing said liquid into engagement with said electrode, said liquidbeing adherent to said electrode and attenuable into a slender columnupon the withdrawal thereof, said electrode being of material resistantto dissolubility by said liquid.

the liquid thereto.'

material resistant to amalgamation with saidmercury.

6. In combination, a container, a conducting liquid in said container,an electrode, means associated with said container for selectivelycreating and abolishing a magnetic eld, and iioat means responsive tothe creation of said magnetic field for displacing said liquid intoengagement with said electrode and responsive to the abolition of saidmagnetic field for attenuating said liqmd into a slender column attachedto said electrode, said liquid comprising a mixture of mercury and ametal rendering said liquid adherent to said electrode upon theseparation of said electrode and said liquid.

'7. In combination, a container, a mercury alloy in said container, anelectrode, means adjacent said container for selectively'creating andabolishing a magnetic field, and float means re-v sponsive to thecreation of said magnetic ileld for displacing said liquid intoengagement with said electrode and responsive to the abolition of saidmagnetic iield for attenuating said mercury alloy into a slender columnattached to said electrode, said mercury alloy comprising a mixture ofmercury and lead.

8. In combination, a container, anelectrode, a conducting liquid in saidcontainer adherent to said electrode, means adjacent said container formeans responsive to the creation of said magnetic ileld for moving saidliquid and said electrode relatively to each other, said electrodehaving a roughened surface whereby to enhance the adhesion of the liquidthereto.

10. In combination, a container, an electrode,

a conducting liquid in said container adherent to said electrode, meansadjacent said container for creating a magnetic field, andfloat-actuated means responsive to the creation of said magnetic ileldformoving said liquid and said lelectrode relatively to each other, saidelectrode having a projecting portion thereonwhereby to assist theadhesion of the liquid thereto. i

11. In combination, a containen'an electrode,l

a conducting liquid in said container adherent to said electrode, meansadjacent said container for creating a magnetic neld, and :Heat-actuatedmeans responsive to the creation of said lmagnetic ileld for moving saidliquid andv said electrode relatively to each other, said electrodehaving an enlarged head whereby to assist the adhesion of 12. Incombination, a container. an electrode.

' a conducting liquid in said container adherent to said electrode.means adiscent said container for creating a magnetic iield, anddoet-achiaized means responsive to the creation o! said magnetic neldior moving said liquid and said electrode relatively to each other. saidelectrode hav- ,ing a tip with a recess therebehind whereby to assistthe Aadhesion oi the liquid thereto.

13.l In combination, a container, an electrode, a conducting liquid insaid container adherent to said electrode. means adJacent said containerfor creating a magnetic field, naat-actuated means responsive to thecreation o! said magnetic neld for moving said liquid and said'electrode relatively to each other, and means at the tip of saidelectrode ior increasing the adhesion of the liquid thereto.

14. In combination, a container, an electrode.

aconductingliquidinsaidcontaineradherent to said electrode. and meansresponsive to the withdrawal oi-said electrode from said liquid forInitially 101mm( l!! donated column' of liquid between laid electrodeand the main`body oi said liquid and for iinaliy severing said elonaatedl5. In combination, a container, an electrode,

v"amixtureoimercury and at leastone othersub-4 ROBERT B. B'IONIR.

